11.3 Cookies

A cookie is a file that resides on the browser's computer (client side). This file defines a single name to a particular value. Unlike parameters, however, the creation of a cookie is a little more difficult.

The following code creates the definition string of a cookie:

$cookieDef = $q->cookie(-name=>'id',-value=>'5923');

In this case, the cookie is called id, and the value is 5923. However, this statement by itself does not create a cookie on the client side. Note that cookie definitions are not a part of the HTML specification, but rather a part of the HTTP standard. In order to instruct the client create a cookie, the cookie definition must be included in the header of an HTTP transmission.

In order to create the cookie, the following statement is needed:

print $q->header(-cookie=>[$cookieDef]);

The syntax [$cookieDef] is ``the reference of a list consisting of a single item of the cookie definition of id.

The following sample code creates a cookie:

#!/usr/bin/perl
use CGI;
use strict;
use warnings;
my $q = new CGI;
my $cookieDef = $q->cookie(-name=>'id',-value=>'someID');
print $q->header(-cookie=>[$cookieDef]);
print $q->start_html;
print 'Check your cookies for a definition of id';
print $q->end_html;

Accessing a cookie is much easier. Since the CGI object $q has full access to the HTTP header, it can extract all the cookie definitions passed to it. Invoking the cookie method without specifying a -value retrieves the value of the named cookie.

Invoking cookie without even specifying a name returns a list of the names of all cookies.